Re: Advice on parallelizing network calls in DoFn

@Lukasz: just a small precision on the bench I shared earlier: the overhead of CompletionStage (implemented with a "fast" flavor) is of < 7% if you ignore the usage of lambda (pass a function instance and not using lambda ref - not sure why the JVM doesn't handles it directly but since a JVM upgrade from the u40 to u144 made a 75% boost thanks to lambda+gc optims, I don't worry much of that part). Here are the raw results I get (Sharing beam one too since I used another computer):

I insist on the good fit of CompletionStage (or any reactive compatible API closer to java 9 maybe) but I had to migrate from a synchronous code to an async one on friday and the migration was not technically hard and brought a lot of benefit since now it can work in any environment (synchronous using toCompletionFuture().get() or asynchronous like akka actors bridging scala future and CompletionStage). For a portable API (I'm not speaking of the beam - language - portable API which is on top of runner from a design point of view) but of the API any runner must integrate with. Integrated with IO (which is the only part giving sense to any pipeline when you think about it) you can scala way more reliable and efficiently optimizing your resources so it would be an awesome fit for a solution like beam IMHO.

Thanks for checking up (I'm working with Josh on this problem). It seems there isn't a built-in process for this kind of use case currently, and that the best process right now is to handle our own bundling and threading in the DoFn. If you had any other suggestions, or anything to keep in mind in doing this, let us know!

Our team has a pipeline that make external network calls. These pipelines are currently super slow, and the hypothesis is that they are slow because we are not threading for our network calls. The github issue below provides some discussion around this:

In beam 1.0, there was IntraBundleParallelization, which helped with this. However, this was removed because it didn't comply with a few BEAM paradigms.

Questions going forward:

What is advised for jobs that make blocking network calls? It seems bundling the elements into groups of size X prior to passing to the DoFn, and managing the threading within the function might work. thoughts?